Protesters are to launch one of the hardest-hitting environmental campaigns for more than a decade over plans to build a new generation of coal-fired power stations in the UK.

Senior scientists, City investors, international leaders and MPs from all parties have joined environmental groups in condemning plans to approve coal plants before there are guarantees that they will be fitted with equipment to stop the release of harmful greenhouse gases.

Supporters of new coal power say Britain desperately needs to fill a looming energy gap and improve security of power supply. But objectors claim it is impossible to build coal stations - the most polluting of all power plants - and still cut pollution.

Without a new technology to control carbon emissions, known as 'carbon capture and storage', the eight plants being planned would account for the entire carbon target that the UK has set itself for the middle of this century, say campaigners. As a result, opposition to construction of new plants has hardened recently with new names joining the growing coalition of opposition every week. Activists' plans are aimed at the government and at Eon, the German-owned company proposing to build the first of the new plants at Kingsnorth in Kent, said Matt Phillips of the European Climate Foundation.

Eon has already been targeted with protests at its offices and outside the headquarters of the Football Association (the company sponsors the FA Cup). The Climate Camp, which last year organised a high-profile sit-in at Heathrow airport, has said that its 2008 camp will probably be at Kingsnorth. Events targeting other coal plant sites in Essex, Northumberland and Fife are expected.

Eon has proposed building two new coal-fired generators next to its current plant at Kingsnorth. The old plant is to be closed because it will fail tough new EU pollution limits that come into force in 2015. The two new 800-megawatt generators would provide the same electricity as the current plant, about enough to supply one and a half million homes.

Eon estimates that the new plants, for which it is awaiting government approval, will each generate greenhouse gases equivalent to eight million tonnes of carbon dioxide a year at full capacity. That compares with 10 million tonnes for the existing plant. Approval for the project, which could cost £1.7bn, would be expected to bring forward applications from other utilities. Campaigners claim there are plans for at least seven new plants - at sites including Tilbury in Essex, Ferrybridge in West Yorkshire and Blyth in Northumberland - generating 10-12 gigawatts of energy, which would pump the equivalent of 50 million tonnes of carbon dioxide into the atmosphere every year.

To help to head off mounting public anger, Eon has entered Kingsnorth for the government-sponsored competition to stage the first commercial trials of carbon capture and storage at the site. Such schemes involve removing carbon dioxide as it is produced by burning coal and then pumping it into spaces under the ground, where it can be stored for thousands of years. Britain is considered to be well suited to such technology, with its many depleted North Sea oil and gas fields.

However, when asked when carbon capture could be taken beyond the pilot project stage, Eon's clean coal business development manager, Andy Read, admitted: 'It's a bit of a guessing game ... It depends on government support.' He also admitted that there is no guarantee that carbon capture, even if it is proved to work, would be fitted to Kingsnorth without the necessary subsidies.

The British government has also come under fire. In the last few months opponents of its promotion of coal power have ranged from the Royal Society, the world's most prestigious scientific organisation, to the powerful Institutional Investors Group on Climate Change, whose members include BNP Paribas, HSBC and the pension funds of the BBC and the Environment Agency.

The UK is looking isolated internationally. Denmark and New Zealand have moratoriums on new coal-fired power stations, Canada has a deadline for new coal generators to have carbon capture fitted by 2018 and California has imposed the same deadline by 2020. US protests have led to 59 of the 151 new coal plants announced last year being dropped and 48 contested in court.